The present invention relates to the device for controlling the stroke length of a slide in a press.
A stroke control device for a press has been known which incorporates, as disclosed in Japanese Patent Examined Publication No. 51-12150 (see related U.S. Pat. No. 3,765,266), a pair of eccentric members. More specifically, this stroke control device has an eccentric shaft portion on a drive shaft, and an eccentric sleeve rotatably mounted on the outer surface of the eccentric shaft portion for a rotation relative thereto, the eccentric sleeve having outer peripheral surface centered at a point which is at an eccentricity from the axis of the eccentric shaft portion. The stroke control device further has a connecting rod the upper end of which rotatably fits around the eccentric sleeve, while the lower end of the connecting rod is connected to a slide of a press. In operation, the eccentric shaft portion is rotated relative to the eccentric sleeve so as to vary the amount of eccentricity and, hence, the stroke length of the slide. The stroke control device further incorporates a releasable locking mechanism which, when the press which drives the rotary shaft operates, locks the eccentric shaft portion and the eccentric sleeve against relative rotation, whereas, when the eccentricity is to be varied, unlocks them from each other so as to allow a relative rotation therebetween.
This known stroke control device, however, suffers from a disadvantages in that the construction is inevitably complicated due to the use of the releasable locking mechanism. Another problem encountered with this known stroke control device is that, since the transmission of the torque from the eccentric shaft portion to the eccentric sleeve is conducted indirectly through the above-mentioned locking mechanism, the rigidity of the path of torque transmission is undesirably reduced to impair the precision in the torque transmission. Still another problem is that the eccentricity cannot be varied linearly due to the fact that the locking mechanism which locks the eccentric shaft portion and the eccentric sleeve against relative rotation is designed to change the locking position non-linearly, i.e., in a stepped manner.